<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 400px;
            height: 200px;
            border: 2px green solid;
            /* border-radius: 100px; */
            /* border-radius: 50%; */
            /* border-radius: 100px; */
            /* border-top-left-radius: 20px;
            border-top-right-radius: 40px;
            border-bottom-right-radius: 20px;
            border-bottom-left-radius: 40px; */
            border-radius: 20px 40px 20px 40px;
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>